From: Christoffer Dall <christoffer.dall@linaro.org> To: Arnd Bergmann <arnd@arndb.de> Cc: Eric Auger <eric.auger@linaro.org>, linux-arm-kernel@lists.infradead.org, eric.auger@st.com, alex.williamson@redhat.com, b.reynal@virtualopensystems.com, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, thomas.lendacky@amd.com, patches@linaro.org, suravee.suthikulpanit@amd.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH] VFIO: platform: AMD xgbe reset module Date: Thu, 15 Oct 2015 17:03:21 +0200 [thread overview] Message-ID: <20151015150321.GA17484@cbox> (raw) In-Reply-To: <37917545.AP0MxbQBzK@wuerfel> On Thu, Oct 15, 2015 at 04:55:13PM +0200, Arnd Bergmann wrote: > On Thursday 15 October 2015 16:46:09 Eric Auger wrote: > > > > > > This is where we'd need a little more changes for this approach. Instead > > > of unbinding the device from its driver, the idea would be that the > > > driver remains bound as far as the driver model is concerned, but > > > it would be in a quiescent state where no other subsystem interacts with > > > it (i.e. it gets unregistered from networking core or whichever it uses). > > > > Currently we use the same mechanism as for PCI, ie. unbind the native > > driver and then bind VFIO platform driver in its place. Don't you think > > changing this may be a pain for user-space tools that are designed to > > work that way for PCI? > > > > My personal preference would be to start with your first proposal since > > it looks (to me) less complex and "unknown" that the 2d approach. > > We certainly can't easily change from one approach to the other without > breaking user expectations, so the decision needs to be made carefully. > > The main observation here is that platform devices are unlike PCI in this > regard because they need extra per-device code. I have argued in the > past that we should not reuse the "VFIO" name here because it's actually > something else. I've adjusted to consider VFIO a general purpose framework for mapping device resources into userspace/VMs, and there are certainly a lot of commonality with both PCI, platform, and potentially other devices for that to make sense. > On the other hand, there are a lot of commonalities, > we just have to make sure we don't try to force the code into one model > that doesn't really work just to make it look more like PCI VFIO. > But given that we now have code for platform device passthrough that works in both QEMU and the kernel side and is actually useful for people, is there a clear technical advantage to go back and rework thaat at this point? Don't get me wrong, I like the idea of having a single driver bound to a platform device, and then that's it, but it just feels like that discussion doesn't necessarily belong in the context of a patch that 'just' seeks to add reset functionality for a specific device for VFIO? -Christoffer
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From: christoffer.dall@linaro.org (Christoffer Dall) To: linux-arm-kernel@lists.infradead.org Subject: [PATCH] VFIO: platform: AMD xgbe reset module Date: Thu, 15 Oct 2015 17:03:21 +0200 [thread overview] Message-ID: <20151015150321.GA17484@cbox> (raw) In-Reply-To: <37917545.AP0MxbQBzK@wuerfel> On Thu, Oct 15, 2015 at 04:55:13PM +0200, Arnd Bergmann wrote: > On Thursday 15 October 2015 16:46:09 Eric Auger wrote: > > > > > > This is where we'd need a little more changes for this approach. Instead > > > of unbinding the device from its driver, the idea would be that the > > > driver remains bound as far as the driver model is concerned, but > > > it would be in a quiescent state where no other subsystem interacts with > > > it (i.e. it gets unregistered from networking core or whichever it uses). > > > > Currently we use the same mechanism as for PCI, ie. unbind the native > > driver and then bind VFIO platform driver in its place. Don't you think > > changing this may be a pain for user-space tools that are designed to > > work that way for PCI? > > > > My personal preference would be to start with your first proposal since > > it looks (to me) less complex and "unknown" that the 2d approach. > > We certainly can't easily change from one approach to the other without > breaking user expectations, so the decision needs to be made carefully. > > The main observation here is that platform devices are unlike PCI in this > regard because they need extra per-device code. I have argued in the > past that we should not reuse the "VFIO" name here because it's actually > something else. I've adjusted to consider VFIO a general purpose framework for mapping device resources into userspace/VMs, and there are certainly a lot of commonality with both PCI, platform, and potentially other devices for that to make sense. > On the other hand, there are a lot of commonalities, > we just have to make sure we don't try to force the code into one model > that doesn't really work just to make it look more like PCI VFIO. > But given that we now have code for platform device passthrough that works in both QEMU and the kernel side and is actually useful for people, is there a clear technical advantage to go back and rework thaat at this point? Don't get me wrong, I like the idea of having a single driver bound to a platform device, and then that's it, but it just feels like that discussion doesn't necessarily belong in the context of a patch that 'just' seeks to add reset functionality for a specific device for VFIO? -Christoffer
next prev parent reply other threads:[~2015-10-15 15:02 UTC|newest] Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top 2015-10-14 15:33 [PATCH] VFIO: platform: AMD xgbe reset module Eric Auger 2015-10-14 15:33 ` Eric Auger 2015-10-14 15:33 ` Eric Auger 2015-10-14 15:38 ` Arnd Bergmann 2015-10-14 15:38 ` Arnd Bergmann 2015-10-15 8:08 ` Eric Auger 2015-10-15 8:08 ` Eric Auger 2015-10-15 8:08 ` Eric Auger 2015-10-15 11:21 ` Arnd Bergmann 2015-10-15 11:21 ` Arnd Bergmann 2015-10-15 11:21 ` Arnd Bergmann 2015-10-15 12:12 ` Christoffer Dall 2015-10-15 12:12 ` Christoffer Dall 2015-10-15 13:59 ` Arnd Bergmann 2015-10-15 13:59 ` Arnd Bergmann 2015-10-15 13:59 ` Arnd Bergmann 2015-10-15 14:46 ` Eric Auger 2015-10-15 14:46 ` Eric Auger 2015-10-15 14:46 ` Eric Auger 2015-10-15 14:55 ` Arnd Bergmann 2015-10-15 14:55 ` Arnd Bergmann 2015-10-15 14:55 ` Arnd Bergmann 2015-10-15 15:03 ` Christoffer Dall [this message] 2015-10-15 15:03 ` Christoffer Dall 2015-10-15 15:49 ` Arnd Bergmann 2015-10-15 15:49 ` Arnd Bergmann 2015-10-15 15:49 ` Arnd Bergmann 2015-10-15 16:35 ` Christoffer Dall 2015-10-15 16:35 ` Christoffer Dall 2015-10-15 16:35 ` Christoffer Dall 2015-10-15 16:53 ` Alex Williamson 2015-10-15 16:53 ` Alex Williamson 2015-10-15 16:53 ` Alex Williamson 2015-10-15 19:42 ` Christoffer Dall 2015-10-15 19:42 ` Christoffer Dall 2015-10-15 19:42 ` Christoffer Dall 2015-10-15 20:26 ` Alex Williamson 2015-10-15 20:26 ` Alex Williamson 2015-10-15 20:26 ` Alex Williamson 2015-10-16 13:06 ` Eric Auger 2015-10-16 13:06 ` Eric Auger 2015-10-16 13:06 ` Eric Auger 2015-10-16 13:26 ` Arnd Bergmann 2015-10-16 13:26 ` Arnd Bergmann 2015-10-16 13:26 ` Arnd Bergmann 2015-10-16 13:56 ` Eric Auger 2015-10-16 13:56 ` Eric Auger 2015-10-16 13:56 ` Eric Auger 2015-10-15 14:20 ` Eric Auger 2015-10-15 14:20 ` Eric Auger 2015-10-15 14:20 ` Eric Auger 2015-10-15 14:28 ` Arnd Bergmann 2015-10-15 14:28 ` Arnd Bergmann 2015-10-15 14:28 ` Arnd Bergmann
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